We need to hold a reference to rdevs while reading and writing to attempt to
correct read errors.  This reference must be taken under an rcu lock.
Signed-off-by: NNeil Brown <neilb@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>